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  • Life Sciences (General)  (5)
  • Aerodynamics  (4)
  • Theoretical, Physical and Computational Chemistry  (4)
  • Mice
  • 1995-1999  (14)
  • 1
    Electronic Resource
    Electronic Resource
    The location of transition states: A comparison of Cartesian, Z-matrix, and natural internal coordinates (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 888-904 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A comparison is made between geometry optimization in Cartesian coordinates, in Z-matrix coordinates, and in natural internal coordinates for the location of transition states. In contrast to the situation with minima, where all three coordinate systems are of comparable efficiency if a reliable estimate of the Hessian matrix is available at the starting geometry, results for 25 different transition states covering a wide range of structural types demonstrate that in practice Z-matrix coordinates are generally superior. For Cartesian coordinates, the commonly used Hessian update schemes are unable to guarantee preservation of the necessary transition state eigenvalue structure, while current algorithms for generating natural internal coordinates may have difficulty handling the distorted geometries associated with transition states. The widely used Eigenvector Following (EF) algorithm is shown to be extremely efficient for optimizing transition states. © 1996 by John Wiley & Sons, Inc.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Molecular energies and properties from density functional theory: Exploring basis set dependence of Kohn - Sham equation using several density functionals (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 775-795 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The performance of four commonly used density functionals (VWN, BLYP, BP91, and Becke's original three-parameter approximation to the adiabatic connection formula, referred to herein as the adiabatic connection method or ACM) was studied with a series of six Gaussian-type atomic basis sets [DZP, 6-31G**, DZVP, TZVP, TZ2P, and uncontracted aug-cc-pVTZ (UCC)]. The geometries and dipole moments of over 100 first-row and second-row molecules and reaction energies of over 300 chemical reactions involving such molecules were computed using each of the four density functionals in combination with each of the six basis sets. The results were compared to experimentally determined values. Based on overall mean absolute theory versus experiment errors, it was found that ACM is the best choice for predictions of both energies of reaction [overall mean absolute theory versus experiment error (MATvEE) of 4.7 kcal/mol with our most complete (UCC) basis set] and molecular geometries (overall MATvEE of 0.92 pm for bond distances and 0.88° for bond angles with the UCC basis set). For routine calculations with moderate basis sets (those of double-ζ type: DZP, 6-31G**, and DZVP) the DZVP basis set was, on average, the best choice. There were, however, examples of reactions where significantly larger basis sets were required to achieve reasonable accuracy (errors ≤ 5 kcal/mol). For dipole moments, ACM, BP91, and BLYP performed comparably (overall MATvEE of 0.071, 0.067, and 0.059 debye, respectively, with the UCC basis set). Basis sets that include additional polarization functions and diffuse functions were found to be important for accurate density functional theory predictions of dipole moments. © 1997 by John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Constrained optimization in delocalized internal coordinates (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 1079-1095 
    Details
    ISSN: 0192-8651
    Keywords: geometry optimization ; constraints ; delocalized internal coordinates ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Using the recently introduced delocalized internal coordinates, in conjunction with the classical method of Lagrange multipliers, an algorithm for constrained optimization is presented in which the desired constraints do not have to be satisfied in the starting geometry. The method used is related to a previous algorithm by the same author for constrained optimization in Cartesian coordinates [J. Comput. Chem., 13, 240 (1992)], but is simpler and far more efficient. Any internal (distance or angle/torsion) constraint can be imposed between any atoms in the system whether or not the atoms involved are formally bonded. Imposed constraints can be satisfied exactly. © 1997 John Wiley & Sons, Inc. J Comput Chem 18:1079-1095, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Predicting the vibrational spectra of some simple fluorocarbons by direct scaling of primitive valence force constants (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1187-1204 
    Details
    ISSN: 0192-8651
    Keywords: vibrational spectra ; SQM force fields ; fluorocarbons ; density functional theory ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Using the scaled quantum-mechanical (SQM) force field approach with direct scaling of individual primitive force constants, we derive optimal scaling factors by a least-squares fit to the experimentally observed fundamentals of some selected “simple” fluorocarbons. We use the derived scaling factors to predict the vibrational spectra of all possible fluoromethanes, fluoroethylenes, fluoroethanes, and monofluoropropenes, proposing a reassignment of some experimental fundamentals. Two separate sets of scaling factors are derived for both traditional Hartree-Fock (HF) calculations and density functional theory (DFT) calculations using the hybrid three-parameter B3-PW91 density functional. With the split-valence 6-31G(d) basis set, our scaling procedure gives an average error of less than 9 cm-1 in the scaled frequencies with the B3-PW91 functional. The average percentage error is around 1%. The HF results are not as good - the average error is 12.6 cm-1 - showing that hybrid density functional SQM schemes are better for predicting vibrational spectra than basic Hartree-Fock.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1187-1204, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
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    Effects of the obese gene product on body weight regulation in ob/ob mice (1995)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1995-07-28
    Description: C57BL/6J mice with a mutation in the obese (ob) gene are obese, diabetic, and exhibit reduced activity, metabolism, and body temperature. Daily intraperitoneal injection of these mice with recombinant OB protein lowered their body weight, percent body fat, food intake, and serum concentrations of glucose and insulin. In addition, metabolic rate, body temperature, and activity levels were increased by this treatment. None of these parameters was altered beyond the level observed in lean controls, suggesting that the OB protein normalized the metabolic status of the ob/ob mice. Lean animals injected with OB protein maintained a smaller weight loss throughout the 28-day study and showed no changes in any of the metabolic parameters. These data suggest that the OB protein regulates body weight and fat deposition through effects on metabolism and appetite.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pelleymounter, M A -- Cullen, M J -- Baker, M B -- Hecht, R -- Winters, D -- Boone, T -- Collins, F -- New York, N.Y. -- Science. 1995 Jul 28;269(5223):540-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurobiology, Amgen, Inc., Thousand Oaks, CA 91320, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7624776" target="_blank"〉PubMed〈/a〉
    Keywords: Adipose Tissue/drug effects ; Analysis of Variance ; Animals ; Blood Glucose/analysis ; Body Composition/drug effects ; Body Temperature/drug effects ; Dose-Response Relationship, Drug ; Drinking/drug effects ; Eating/*drug effects ; Energy Metabolism/drug effects ; Female ; Insulin/blood ; Leptin ; Mice ; Mice, Inbred C57BL ; Mice, Obese ; Motor Activity/drug effects ; Obesity/genetics/*physiopathology ; Oxygen Consumption/drug effects ; Proteins/genetics/*pharmacology ; Recombinant Proteins/pharmacology ; Weight Loss/*drug effects
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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    PAPER CURRENT
  • 6
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    Melatonin and cortisol assessment of circadian shifts in astronauts before flight (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Melatonin and cortisol were measured in saliva and urine samples to assess the effectiveness of a 7-day protocol combining bright-light exposure with sleep shifting in eliciting a 12-hr phase-shift delay in eight U.S. Space Shuttle astronauts before launch. Baseline acrophases for 15 control subjects with normal sleep-wake cycles were as follows: cortisol (saliva) at 0700 (0730 in urine); melatonin (saliva) at 0130 (6-hydroxymelatonin sulfate at 0230 in urine). Acrophases of the astronaut group fell within 2.5 hr of these values before the treatment protocols were begun. During the bright-light and sleep-shifting treatments, both absolute melatonin production and melatonin rhythmicity were diminished during the first 3 treatment days; total daily cortisol levels remained constant throughout the treatment. By the fourth to sixth day of the 7-day protocol, seven of the eight crew members showed phase delays in all four measures that fell within 2 hr of the expected 11- to 12-hr shift. Although cortisol and melatonin rhythms each corresponded with the phase shift, the rhythms in these two hormones did not correspond with each other during the transition.
    Keywords: Life Sciences (General)
    Type: Journal of pineal research (ISSN 0742-3098); Volume 18; 3; 141-7
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    NASA TECHNICAL REPORTS
  • 7
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    Simulated Inlet Unstart and Nacelle/Diverter Effects for the Boeing Reference H Configuration (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The Boeing Reference H configuration was tested in the NASA Ames 9x7 Supersonic Wind Tunnel. A simulated unstarted inlet was evaluated as well as the aerodynamic performance of the configuration with and without nacelle and diverter components. These experimental results were compared with computational results from the unstructured grid Euler flow solver AIRPLANE. The comparisons between computational and experimental results were good, and demonstrated that the Euler code is capable of efficiently and accurately predicting the changes in the aerodynamic coefficients associated with inlet unstart and the effects of the nacelle and diverter components.
    Keywords: Aerodynamics
    Type: First NASA/Industry High-Speed Research Configuration Aerodynamics Workshop; Part 3; 1285-1325; NASA/CP-1999-209690/PT3
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    NASA TECHNICAL REPORTS
  • 8
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    Airplane Mesh Development with Grid Density Studies (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Automatic Grid Generation Wish List Geometry handling, including CAD clean up and mesh generation, remains a major bottleneck in the application of CFD methods. There is a pressing need for greater automation in several aspects of the geometry preparation in order to reduce set up time and eliminate user intervention as much as possible. Starting from the CAD representation of a configuration, there may be holes or overlapping surfaces which require an intensive effort to establish cleanly abutting surface patches, and collections of many patches may need to be combined for more efficient use of the geometrical representation. Obtaining an accurate and suitable body conforming grid with an adequate distribution of points throughout the flow-field, for the flow conditions of interest, is often the most time consuming task for complex CFD applications. There is a need for a clean unambiguous definition of the CAD geometry. Ideally this would be carried out automatically by smart CAD clean up software. One could also define a standard piece-wise smooth surface representation suitable for use by computational methods and then create software to translate between the various CAD descriptions and the standard representation. Surface meshing remains a time consuming, user intensive procedure. There is a need for automated surface meshing, requiring only minimal user intervention to define the overall density of mesh points. The surface mesher should produce well shaped elements (triangles or quadrilaterals) whose size is determined initially according to the surface curvature with a minimum size for flat pieces, and later refined by the user in other regions if necessary. Present techniques for volume meshing all require some degree of user intervention. There is a need for fully automated and reliable volume mesh generation. In addition, it should be possible to create both surface and volume meshes that meet guaranteed measures of mesh quality (e.g. minimum and maximum angle, stretching ratios, etc.).
    Keywords: Aerodynamics
    Type: 1998 NASA High-Speed Research Program Aerodynamic Performance Workshop; Volume 1; Part 1; 75-145; NASA/CP-1999-209692/VOL1/PT1
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Changes in gravity inhibit lymphocyte locomotion through type I collagen (1997)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Immunity relies on the circulation of lymphocytes through many different tissues including blood vessels, lymphatic channels, and lymphoid organs. The ability of lymphocytes to traverse the interstitium in both nonlymphoid and lymphoid tissues can be determined in vitro by assaying their capacity to locomote through Type I collagen. In an attempt to characterize potential causes of microgravity-induced immunosuppression, we investigated the effects of simulated microgravity on human lymphocyte function in vitro using a specialized rotating-wall vessel culture system developed at the Johnson Space Center. This very low shear culture system randomizes gravitational vectors and provides an in vitro approximation of microgravity. In the randomized gravity of the rotating-wall vessel culture system, peripheral blood lymphocytes did not locomote through Type I collagen, whereas static cultures supported normal movement. Although cells remained viable during the entire culture period, peripheral blood lymphocytes transferred to unit gravity (static culture) after 6 h in the rotating-wall vessel culture system were slow to recover and locomote into collagen matrix. After 72 h in the rotating-wall vessel culture system and an additional 72 h in static culture, peripheral blood lymphocytes did not recover their ability to locomote. Loss of locomotory activity in rotating-wall vessel cultures appears to be related to changes in the activation state of the lymphocytes and the expression of adhesion molecules. Culture in the rotating-wall vessel system blunted the ability of peripheral blood lymphocytes to respond to polyclonal activation with phytohemagglutinin. Locomotory response remained intact when peripheral blood lymphocytes were activated by anti-CD3 antibody and interleukin-2 prior to introduction into the rotating-wall vessel culture system. Thus, in addition to the systemic stress factors that may affect immunity, isolated lymphocytes respond to gravitational changes by ceasing locomotion through model interstitium. These in vitro investigations suggest that microgravity induces non-stress-related changes in cell function that may be critical to immunity. Preliminary analysis of locomotion in true microgravity revealed a substantial inhibition of cellular movement in Type I collagen. Thus, the rotating-wall vessel culture system provides a model for analyzing the microgravity-induced inhibition of lymphocyte locomotion and the investigation of the mechanisms related to lymphocyte movement.
    Keywords: Life Sciences (General)
    Type: In vitro cellular & developmental biology. Animal (ISSN 1071-2690); Volume 33; 5; 398-405
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    NASA TECHNICAL REPORTS
  • 10
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    Functional and cellular adaptations of rodent skeletal muscle to weightlessness (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper describes the affects of microgravity upon three key cellular levels (functional, protein, and mRNA) that are linked to one another. It is clear that at each of these levels, microgravity produces rapid and substantial alterations. One of the key challenges facing the life science community is the development of effective countermeasures that prevent the loss of muscle function as described in this paper. The development of optimal countermeasures, however, awaits a clearer understanding of events occurring at the levels of transcription, translation, and degradation.
    Keywords: Life Sciences (General)
    Type: Journal of Gravitational Physiology, Volume 2, No. 1; 39-42
    Format: text
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    NASA TECHNICAL REPORTS
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